1. Field of the Invention
The present invention relates to a flame retardand blend of three types of polymer components. The blend has good impact resistance and a high heat deflection temperature so as to be useful as an outdoor construction material.
2. Description of the Prior Art
Impact resistant, weatherable polymer compositions comprising acrylate, styrene, and acrylonitrile components are known. Thus, U.S. Pat. No. 3,944,631 to A.J. Yu et al., which discloses one of the components of the type of blend of the present invention, describes an interpolymer comprising: (a) crosslinked (meth)acrylate; (b) crosslinked styrene-acrylonitrile; and (c) uncrosslinked styrene-acrylonitrile polymeric components. This material is said to have superior weather resistance as compared to ABS polymers and is only taught for use by itself without blending with other polymeric materials.
Two-component blends of a thermoplastic polymer (such as PVC or CPVC) and an acrylate-containing impact modifier, heat distortion temperature improver, and process aid are described in U.S. Pat. No. 3,655,826 to R.P. Fellmann et al. Two-component blends of CPVC and MBS (styrene-methyl methacrylate-butadiene) resins are described in U.S. Pat. No. 3,646,163 to S. Taima et al., with the use of ABS in such blends being discouraged.
Finally, three-component blends of CPVC, PVC and either ABS or MBS are suggested in U.S. Pat. No. 3,639,526 to M. Kameishi. The latter two components are present in lower amount than the CPVC resin and are merely intended to be impact modifiers for the CPVC component.